I can certainly identify with the author's experiences, but must point out that most user oriented distros are incredibly easy to install, unlike those chosen by the author. So this should not be considered an average user's linux install. The author is not an average user with average needs, but still could have avoided all the problems listed by simply asking questions. Most linux users are very eager to give advice or assistance. Anyway, here is my advice:

If you are new to linux and setting up a multiboot system, use a separate hard drive for linux or be prepared for the possibility of messing something up.

Put the Linux drive in Primary Master position, so the installer does not have to modify the Windows mbr. If you mess up, you can always move the Windows drive back to Primary Master.

If think you would like to switch distros occasionally (every few months on the laptop I'm on now), make sure you create a /home partition, so you never lose your user data. You will just format and install to the / partition, and preserve your /home.